Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$204.85	6.643%	$218.4582	$218.46	$218.45	$218.50
Purchase #2	$127.68	12.378%	$143.4842	$143.48	$143.50	$143.50
Purchase #3	$53.59	6.434%	$57.038	$57.04	$57.05	$57.00
Purchase #4	$52.88	7.307%	$56.7439	$56.74	$56.75	$56.70
Purchase #5	$121.60	12.283%	$136.5361	$136.54	$136.55	$136.50
Purchase #6	$202.26	7.239%	$216.9016	$216.90	$216.90	$216.90
Purchase #7	$241.41	12.427%	$271.41	$271.41	$271.40	$271.40
7 purchase totals =	$1,004.27		$1,100.5720	$1,100.57	$1,100.60	$1,100.50